Prevalence of Fasciola gigantica infection in slaughtered animals in south-eastern Lake Chad area in relation to husbandry practices and seasonal water levels

Background: Fasciolosis has been described in sub-Saharan Africa in many accounts, but the latest reports from Chad are from the 1970s. Mobile pastoralists perceive liver parasites as a significant problem and think that proximity to Lake Chad can lead to infection. This study aimed to assess the importance of liver fluke infections in mobile pastoralists' livestock in the south-eastern Lake Chad region. In 2011, all animals presented at three slaughter slabs near Gredaya in the south-eastern Lake Chad area were examined for infection with Fasciola spp. during routine meat inspections. Results: This study included 616 goats, 132 sheep and 130 cattle. The prevalence of adult Fasciola gigantica was 68% (CI 60-76%) in cattle, 12% (CI 10-16%) in goats and 23% (CI 16-30%) in sheep. From all infected animals (n =200), 53% (n =106) were classified as lightly infected with 1-10 parasites, 18% (n =36) as moderately infected with 11-100 parasites and 29% (n =58) as heavily infected with more than 100 parasites per animal. Animals grazing close to the shores of Lake Chad had a much higher risk of infection (prevalence =38%; n =329) than animals not feeding at the lake (n =353), with only one goat being positive (prevalence =0.28%). The ethnic group of the owner was a strong determinant for the risk of infection. Ethnic group likely served as a proxy for husbandry practices. Geospatial distribution showed that animals originating from areas close to the lake were more likely to be infected with F. gigantica than those from more distant areas. Conclusions: Livestock belonging to ethnic groups which traditionally stay near surface water, and which were reported to feed near Lake Chad, have a high risk of infection with F. gigantica. Pastoralist perception of fasciolosis as a priority health problem was confirmed. Regular preventive and post-exposure treatment is recommended for animals grazing near the lake. However, further economic analysis is needed.